1. Field of Invention
The present invention relates to fuzes for submunissions of the type which are disbursable by a vehicle such as a projectile or carrier shell, and in particular, to a self-destructing fuze that automatically self-destructs or self-neutralizes the submunition if the primary mode of detonation fails.
2. Description of Related Art
For many years, submunitions included in the family of Improved Conventional Munitions (ICM) employed a simple, low cost point detonating fuze for initiating a main charge upon impact. Reliability of the fuze was in the 95% range, meaning fairly large quantities of submunitions would not function for various reasons. This failure rate of about 5% presents both an environmental and a humanitarian hazard. Hazardous duds (e.g., armed but unexploded submunitions) remained on the battle field indefinitely and with potentially undesirable consequences to friendly troops and/or civilians.
The currently used M223 fuze incorporated unique and effective safety features for personnel and property protection during the manufacturing and loading process. Key among these safety features is a stabilizer ribbon attached to an arming screw that, in its engaged position, locks a detonator-containing slide in an unaligned position, thereby preventing any possible contact of a primary firing pin with the detonator. Upon deployment of the submunition from its carrier (e.g., howitzer projectile) the stabilizer ribbon becomes exposed to the air stream wind resistance and unfurls. The combination of wind resistance, induced spin of the submunition, and/or vibration causes the submunition to rotate relative to the ribbon, causing an arming screw to back out, which in turn releases a spring loaded slide that shifts, allowing the firing pin to align with the detonator. Upon impact, the firing pin, which is typically attached to a small weight, drives into the detonator causing initiation of the main charge.
In the case of projectile carrier, the entire submunition is spinning at a very high rate at ejection and the ribbon's resistance to spinning causes the arming screw to back out. However, a missile is a non-spin carrier so rotation is not available to arm the unit. Instead, the arming screw backs out because of the vibration induced as the submunition descends. That is, a loose fit between the arming screw and weight allows the arming screw to back out, which releases the spring loaded slide to align the firing pin with the detonator.
The failure of the armed submunitions described above results in hazardous duds. Incidence of death and injury to innocent victims from such hazardous duds, coupled with an international moratorium on antipersonnel mines, demonstrates a need to find a solution that would minimize these residuals on the battle field. It would be beneficial to provide a Self-Destruct Fuze (SDF) that, in the event of failure of the fuze in the primary mode, would cause a secondary action to either explode the entire submunition or at least destroy the detonator (e.g., sterilize the submunition, otherwise referred to as sterilization).
U.S. Pat. No. 5,373,790, to Chemiere, et al., discloses a mechanical system for self-destruction of a submunition, having a warhead initiated by a pyrotechnic sequence, a main striker and a priming device composed of a slide movable between a safety position and an armed position, and which has a device for priming the charge. The self-destruction system includes a secondary striker mounted inside a receptacle of the slide, and a control device that releases the secondary striker after a delay. The secondary striker is integral with a holding element held abutting a seat by the urging of an arming spring. The control device of the secondary striker has a corrosive agent stored in a glass ampoule that, when broken by the holding element, chemically attacks the holding element to release it from its seat. When the holding element is released, the arming spring moves the secondary striker to contact the detonator and destroy the munition.
U.S. Pat. No. 4,653,401, to Gatti, discloses a self-destructing fuze having a first striker member movable within the body of the fuze and able to come into contact with a detonator to cause it to explode, and a slide that is movable in a direction substantially orthogonal to the direction in which the first striker member is movable. A second striker member is disposed in the slide, and is movable from a first position in which it elastically deforms a spring and is held at a predetermined distance from the detonator, to a second position in which it comes into contact with the detonator to cause it to explode. The movement of the second striker member is delayed by a section of wire that under a force exerted by the spring is plastically deformed over time. The plastic deformation eventually frees the second striker member allowing its movement to the second position and against the detonator to cause it to explode.
U.S. Pat. No. 5,932,834, to Lyon, et al., discloses an auto-destruct fuze that provides a primary mode detonator and a delayed auto-destruct/self-neutralize mode detonator for a grenade. The mechanics for the primary mode detonator is similar to the M223 fuze. Operation of the auto-destruct/self-neutralize is based on a Liquid Annular Orifice Device (LAOD) that is released from a locked position upon expulsion of the LAOD from a storage container. The LAOD moves slowly under the urging of a spring and eventually releases a clean-up firing pin which activates a clean-up detonator to activate the primary mode detonator and destructs or self-neutralizes the grenade.
U.S. Pat. No. 4,998,476, to Rüdenauer, et al., discloses a fuze for a bomblet including a slide having a detonator triggered in response to an impact and which undergoes a transition during the free flight of the bomblet from a safe position into an armed position. The slide also includes a hydraulic or pneumatic cylinder-piston retarding device and a spring biased self-destruct pin which is operatively coupled to the device and has a self-destruct detonator associated therewith. The retarding device is freed upon movement of the slide to the armed position, and releases the movement of the self-destruct pin after a time delay to trigger the self-destruct detonator and, if needed, the primary detonator.
Numerous variations of self-destruct (SD) devices, working in conjunction with proven safety features of the stabilizer ribbon arming screw, and sliding arrangement have been developed with various degrees of success. In one variant, the SD feature centers around a microelectronic battery and circuit with a complicated attendant initiating device. Two other variants employ a critical pyrotechnic delay column to achieve the necessary time lapse. Even if successful, the critical manufacturing process and high costs of these candidates raise long term and expensive productabilty concerns.
Even with the current self-destruct fuze development, it would still be beneficial to provide reliable low-cost and improved self-destruct delay devices or mechanisms for automatically destroying or self-neutralizing submunitions after a time delay to minimize undesirable consequences to friendly troops and/or civilians. All references cited herein are incorporated herein by reference in their entireties.